Defluxing of Copper Pillar Bumped Flip-Chips - Technical Article
Flip-chip technology has become increasingly prevalent within the electronics industry due to its lower cost, increased package density, improved performance while maintaining or improving circuit reliability, and increased I/O density.
This technology is a method for interconnecting semiconductor devices such as IC chips and MEMS to external circuitry with solder bumps that have been deposited onto the chip pads. However, solder bump technology has proven to be problematic below 125μm pitch as it is challenging to manufacture and assemble. As the pitch is reduced, both standoff height and joint reliability decrease, and the risk of shorts are increased.
Given this, traditional solder bumps are being replaced by copper pillar technology. Used as a first-level interconnect, copper pillar technology is increasing in popularity. Copper pillar technology has been documented to be efficient to pitches of 80 μm and appears to be promising down to pitches of 40μm. Along with the reduced pitch, copper pillar brings several other benefits, including improved electrical performance. This technology is becoming popular since it allows for smaller devices, greater control of standoff height, and reduces the number of package substrate layers which reduces cost.
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